Process for the preparation of group ii and group iii lube base oils

ABSTRACT

A process for the preparation of Group II and Group III lube oil base stocks wherein liquid-continuous aromatics saturation is used to treat lube hydrocrackate. The treated hydrocrackate is then be sent to dewaxing unit and then optionally to a hydrotreating step.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Non-provisional application that claims priority to U.S.Provisional Application No. 61/360,113 filed Jun. 30, 2010, which isherein incorporated by reference in its entirety.

FIELD

This disclosure relates to the preparation of Group II and Group IIIlube base oils wherein liquid-continuous aromatics saturation is used totreat a lube hydrocrackate. The treated hydrocrackate is then dewaxedand then optionally hydrofinished.

BACKGROUND

Crude petroleum is distilled and fractionated into many products such asgasoline, kerosene, jet fuel, asphaltenes, and the like. One portion ofthe crude petroleum forms the base of lubricating base oils used in,inter alia, the lubricating of internal combustion engines. Lube oilusers are demanding ever increasing base oil quality, and refiners arefinding that their available equipment is becoming less and less able toproduce base oils that meet these higher quality specifications. Newprocesses are required to provide refiners with the tools for preparinghigh quality modern base oils, particularly using existing equipment atlower cost and with safer operation.

Finished lubricants used for such things as automobiles, diesel engines,and industrial applications generally are comprised of a lube base oiland additives. In general, a few lube base oils are used to produce awide variety of finished lubricants by varying the mixtures ofindividual lube base oils and individual additives. Typically, lube baseoils are simply hydrocarbons prepared from petroleum or other sources.Lube base oils are normally manufactured by making narrow cuts of vacuumgas oils from a crude vacuum tower. The cut points are set to controlthe final viscosity and flash point of the lube base oil.

Group I base oils, those with greater than 300 ppm sulfur and 10 wt. %aromatics are generally produced by first extracting a vacuum gas oil(or waxy distillate) with a polar solvent, such as N-methyl-pyrrolidone,furfural, or phenol. The resulting waxy raffinates produced from solventextraction process are then dewaxed, either catalytically with the useof a dewaxing catalyst such as ZSM-5, or by solvent dewaxing. Theresultant base oil may be hydrofinished to improve color and otherlubricant properties.

Group II base oils, those with less than 300 ppm sulfur and 10 wt. %aromatics, and with a viscosity index range of 80-120, are typicallyproduced by hydrocracking followed by selective catalytic dewaxing andhydrofinishing. Hydrocracking upgrades the viscosity index of theentrained oil in the feedstock by ring cracking and aromaticssaturation. The degree of aromatics saturation is limited by the hightemperature of the hydrocracking stage. In the second stage of theprocess, the hydrocracked oil is dewaxed, either by solvent dewaxing orby catalytic dewaxing, with catalytic dewaxing typically being thepreferred dewaxing technology. The dewaxed oil is then preferablyhydrofinished at mild temperatures to remove polynuclear aromatics whichwere not converted in the first stage and the dewaxing stage and whichhave a strongly detrimental impact on lube base oil quality.

Group III base oils have the same sulfur and aromatics specifications asGroup II base stocks but have viscosity indices above 120. Thesematerials are manufactured with the same type of catalytic technologyemployed to produce Group II base oils but with either the hydrocrackerbeing operated at much higher severity, or with the use very waxyfeedstocks.

A typical lube hydroprocessing plant consists of two primary processingstages. In the lead stage, a feedstock, typically a vacuum gas oil,deasphalted oil, processed gas oils, or any combination of thesematerials, is hydrocracked or solvent extracted. The hydrocracking stageupgrades the viscosity index of the entrained oil in the feedstock byring cracking and aromatics saturation. The degree of aromaticssaturation is limited by the high temperature of the hydrocrackingstage. In a second stage, the hydrocracked oil is dewaxed, preferablywith the use of a highly shape-selective catalyst capable of waxconversion by isomerization. The dewaxed oil can be subsequentlyhydrofinished at mild temperatures to remove polynuclear aromatics thatwere not converted in the upstream hydrocracking and dewaxing stages andwhich have a strongly detrimental impact on lube base oil quality.Operation of the final hydrofinishing step is optimized to convertpolynuclear aromatics; conversion of these species and significantconversion of one ring and two ring aromatics cannot be accomplished inthe final hydrofinishing step because of its low operating temperature.

Group II or III base stocks specifications limit total aromatics contentto less than 10 wt. %. However, specific marketing requirements forthese materials can be more demanding limiting aromatics contents to 5%or even less. The processing of heavier, more aromatics feedstocksrequires a higher degree of aromatics conversion in the hydrocrackingand dewaxing zones, which is difficult for conventional lube processingtechnology. There is a need in the art for improved process technologyto allow for the use of heavier feeds for the production of Group II andGroup III base stocks.

SUMMARY

In accordance with the present disclosure there is provided a processfor the production of lube base oils, which process comprising:

i) hydrocracking a lube oil feedstock having a boiling point above 600°F. and containing polycyclic aromatics in the presence of hydrogen and ahydrocracking catalyst to produce a hydrocrackate having a boiling pointabove 600° F. which hydrocrackate contains a lesser amount of polycyclicaromatics than said lube oil feedstock;

ii) hydrotreating at least a portion of said hydrocrackate in thepresence of an aromatics saturation catalyst under effective aromaticssaturation conditions in a liquid-continuous reactor to form ahydrotreated hydrocrackate having a waxy paraffinic component; and

iii) catalytically dewaxing said hydrotreated hydrocrackate in thepresence of hydrogen and a dewaxing catalyst under effective dewaxingconditions including a temperature from 550° F. to 800° F. and apressure up to 2200 psig and at an effective contact time of feed tocatalyst that will remove at least a portion of the waxy paraffiniccomponents by isomerization to less waxy iso-paraffinic components,thereby producing a lube base oil containing at least 90 wt. %saturates, less than 0.03 wt. % sulfur and a viscosity index of at least80.

In a preferred embodiment, the dewaxed liquid effluent is hydrofinished,by treating it with a hydrofinishing catalyst, in the presence ofhydrogen and at effective hydrofinishing conditions that result in theremoval of at least a portion of any remaining aromatics, heteroatoms,or both.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE hereof is a simplified flow diagram of a preferred embodimentof the present disclosure showing the primary process units.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

The present disclosure is directed to the preparation of Group II andGroup III lube base oils. API Publication 1509: Engine Oil Licensing andCertification System, “Appendix E-API Base Oil InterchangeabilityGuidelines for Passenger Car Motor Oil and Diesel Engine Oils” describesbase stock categories. A Group II base oil will contain greater than orequal to 90 wt. % saturates and less than or equal to 0.03 wt. % sulfurand will have a viscosity index (VI) greater than or equal to 80 andless than 120. A Group III base oil will contain greater than or equalto 90 wt. % saturates and less than or equal to 0.03 wt. % sulfur andwill have a VI greater than or equal to 120. The VI of an oil is anarbitrary relative measure of the oil's change in viscosity withtemperature. The smaller the change in viscosity of an oil at a giventemperature the higher the VI value of the oil. A high VI is desirablein high quality motor oils. The term “viscosity index” (VI) refers tothe measurement defined by ASTM D2270.

Lube hydroprocessing refineries are continually challenged to increasethroughput and to process more refractory feedstocks. The limitation onrefineries to accomplish these objectives is increasingly becoming therefinery's ability to convert aromatics in the feed to meet Group IIspecification (10 wt. % max) or specific market requirements.

Both increasing through-put and increasing feed difficulty, work againsthigh aromatics conversion. Increasing throughput and feed aromaticsincreases the temperature at which hydrocracking must be operated. Thislimits the amount of aromatics conversion that can occur because ofequilibrium constraints. Additionally, increasing throughput anddeclining feed quality, while increasing the aromatics content of thematerial entering the dewaxing/hydrotreating zone, also increases thedegree of nitrogen slip to this stage. Increases in both aromatics andnitrogen result in lower dewaxing catalyst life, high dewaxing catalystoperating temperature, and less ability of the dewaxing stage to convertaromatics remaining from the hydrocracking zone.

U.S. Pat. No. 5,951,848 teaches the use of a hydrotreating catalyst inthe dewaxing reactor upstream of the dewaxing catalyst. The purposes ofthis hydrotreating catalyst, which typically contains a noble metal onan amorphous support (alumina or silica-alumina), are to: a) reduce thearomatics content of the oil reaching the dewaxing catalyst as aromaticshave been shown to detrimentally impact dewaxing catalyst life; and b)decouple aromatics saturation from dewaxing so that the exothermassociated with aromatics conversion becomes isolated from the dewaxingcatalyst (which has aromatics saturation capability). This allows thedewaxing catalyst to operate more isothermally which increases its lifeand its selectivity for base oil production.

Increasing rate and feed refractoriness requires greater dewaxingcatalyst volume to maintain cycle length. In a conventionalconfiguration, this would result in displacement of some of thehydrotreating catalyst in the dewaxing reactor which results in lessability to convert aromatics. A solution is represented by the presentdisclosure with the addition of a hydrocracking reactor, particularly aliquid-continuous reactor, upstream of the dewaxing.

A typical process scheme for manufacturing Group II base oils fromvacuum gas oils includes combining a lube oil feedstock with hydrogen,typically at a rate of 2,000 to 10,000 standard cubic feet per barrel(scf/bbl), and hydrocracking it in the presence of hydrogen and ahydrocracking catalyst, typically in a multi-bed reactor, or in multiplereactors. Hydrocracking is typically operated at a temperature from 600to 850° F. with a liquid flow rate to hydrocracking catalyst volume from0.2 to 5 liquid hourly space velocity.

The nature of hydrocracking catalysts are known to those having ordinaryskill in the art and typically contain at least one Group VIII metal,including non-noble metals such as Co and Ni, and noble metals such asPt and Pd, in combination with at least one Group VIB metal, preferablyselected from Mo and W. These metals are supported on a refractorysupport such as alumina, amorphous silica-alumina, structuredaluminosilicates such as zeolites, or a combination of supports. Suchcatalysts are described in U.S. Pat. No. 3,852,207, which isincorporated herein by reference. The non-noble metals (such asnickel-molybdenum) are usually present in the final catalyst compositionas oxides.

Preferred non-noble metal catalyst compositions contain in excess of 5wt. %, preferably 5 wt. % to 40 wt. % molybdenum and/or tungsten, and atleast 0.5 wt. %, and generally 1 wt. % to 15 wt. % of nickel and/orcobalt determined as the corresponding oxides, and are converted tosulfide form prior to use. The noble metal (such as platinum) catalystscontain in excess of 0.01 wt. % metal, preferably between 0.1 wt. % to 1wt. % metal. Combinations of noble metals may also be used, such asmixtures of platinum and palladium. All Groups referred to in thisdocument are groups of the a Periodic Table of the Elements, such as theSargent-Welch Periodic Table of the Elements copyrighted in 1968 by theSargent-Welch Scientific Company.

The product from the hydrocracking reactions is separated into gaseousproducts, liquid products, and a heavy hydrocrackate. Off-gas from thehydrocracking process is usually purified of contaminant gases such asammonia and H₂S before being recycled. The hydrocrackate liquid iseither stored in tankage before further processing, or is fed directlyto a second stage of the process. Aromatics reduction during thehydrocracking stage will vary with operating temperature, as set by feedquality and catalyst life within its operating cycle. Aromaticsreduction will preferably be at least 50% of the total aromatics in thefeed. The pour point of the hydrocrackate will typically be above 80°F., and can often be above 120° F.

The hydrocracking reactor operation is controlled primarily to meet afinished base oil VI target. Aromatics and nitrogen conversion are alsoparameters, but have secondary importance in the control of thehydrocracking stage. Because the hydrocracking and dewaxing stages oftenoperate at elevated temperatures that do not favor the conversion ofcondensed aromatic species, a final low temperature hydrofinishing stepis typically employed to reduce the polynuclear aromatics content toimprove oxidation stability and color. Because the hydrofinishing stageoperates at low temperature, it is not particularly effective atreducing total aromatics. As described above, overall aromaticsconversion occurs over each step of the catalytic lubes refiningprocess. Increasing the refractory nature of the feedstock, orincreasing throughput, increases the temperature required for both thehydrocracking and dewaxing stages. This makes it more difficult toconvert aromatics by conventional processing techniques.

Feedstocks suitable for use herein may be one or a combination ofrefinery streams having a normal boiling point of at least 600° F. (316°C.), although the process is also useful with oils that have initialboiling points as low as 435° F. (224° C.). By having a normal boilingpoint of at least 600° F. (316° C.) is meant that 85% by volume of thefeedstock has a boiling point at atmospheric pressure of at least 600°F. (316° C.). While higher boiling lube oil feedstocks can be processedin accordance with the present disclosure, the preferred feedstock willhave a boiling range such that at least 85% by volume of the feedstockhas a normal boiling point of at most 1250° F. (677° C.), and morepreferably at most 1100° F. (593° C.). Such feedstocks, particularlyvacuum gas oils, will contain from 35 wt. % to 70 wt. % aromatics, atleast 40% of them being 2-ring and higher aromatics. Representativefeedstocks that can be treated using the present process include gasoils and vacuum gas oils (VGO), hydrocracked gas oils and vacuum gasoils, deasphalted oils, slack waxes, foots oils, coker tower bottoms,reduced crude, vacuum tower bottoms, deasphalted vacuum resids, FCCtower bottoms and cycle oils and raffinates from a solvent extractionprocess. The nitrogen, sulfur and saturate contents of these feeds willvary depending on a number of factors. The preferred feedstocks for thepresent disclosure will have an entrained oil viscosity index of greaterthan 30. In a more preferred embodiment, the entrained oil in thefeedstock will have a viscosity index in the range of 40 to 60.

The process of the present disclosure is better understood withreference to the FIGURE hereof. This FIGURE illustrates the primarypieces of equipment for practicing the present disclosure and does notshow ancillary equipment, such as valves, pumps, compressors, heatexchanger, heaters and the like. The function of such equipment is wellknown to those skilled in the art. A lube oil feedstock is conducted tohydrocracking reactor 100 via line 10. Makeup hydrogen can be added asneed via line 11. Feed molecules are reshaped and some are cracked intosmaller molecules in hydrocracking reactor 100. Almost all of the sulfurand nitrogen are removed, and aromatic compounds are saturated withhydrogen. Molecular reshaping occurs as isoparaffins and saturated ringcompounds are formed. These compounds have high VIs and low pour points.However, waxy compounds, chiefly normal-paraffins are largely unaffectedby hydrocracking and must be removed in a subsequent process in order toreduce the pour point.

The resulting hydrocracker effluent is conducted via line 12 to firstseparation zone 200, which is preferably a hot high-pressure separatorwherein a gaseous effluent fraction is separated from a liquid effluentfraction. The gaseous effluent fraction, via line 14, can be treated toremove acidic components and recycled to the hydrocracking reactor 100.The liquid hydrocrackate effluent from first separation zone 200 ispassed via line 16 to liquid-continuous aromatics saturation reactor300. Makeup hydrogen, as needed, can be introduced via line 17. It willbe understood that the makeup hydrogen can be added at any suitablepoint to the feed line or even directly into the reactor 300. It is alsowithin the scope of this disclosure that the liquid effluent fromseparation zone 200 can be contacted with a fraction of recycle liquideffluent from liquid-continuous aromatics saturation reactor 300, eitherdirectly from the reactor, or from a low pressure separator (not shown).

The liquid effluent from separation zone 200 is also contacted with ahydrogen-rich treat gas in sufficient quantity and in the presence of asuitable aromatics saturation catalyst to saturate at least a fractionof the aromatics of the liquid effluent entering reactor 300. Catalystssuitable for use in liquid-continuous aromatics saturation reactor 300can comprise a support component and one or catalytic metal componentsof metal from Groups VIB (Mo, W, Cr) and/or non-noble (Co, Mo) and noblemetals, such as Pt and Pd from Group VIII. The metal or metals may bepresent from as little as 0.1 wt % for noble metals, to as high as 40 wt% of the catalyst composition for supported non-noble metals. Preferredsupport materials are low in acid and include, for example, amorphous orcrystalline metal oxides such as alumina, silica, silica alumina,titania, zirconia, silica-alumina and ultra large pore crystallinematerials known as mesoporous crystalline materials, of which MCM-41 isa preferred support component. The preparation and use of MCM-41 isdisclosed, for example, in U.S. Pat. Nos. 5,098,684, 5,227,353 and5,573,657, both of which are incorporated herein by reference.

Bulk multimetallic catalysts can also be used for aromatics saturationin the practice of the present disclosure. Such catalysts are describedin U.S. Pat. Nos. 6,156,695; 6,162,350; and 6,299,760, all of which areincorporated herein by reference. The catalysts described in thesepatents are bulk multimetallic catalysts comprised of at least one GroupVIII non-noble metal and at least two Group VIB metals, wherein theratio of Group VIB metal to Group VIII non-noble metal is from 10:1 to1:10. These catalysts are prepared from a precursor having the formula:

(X)_(a)(Mo)_(b)(w)_(d)O_(z)

where X is a Group VIII non noble metal, wherein the molar ratio of anda, b, and c, are such that 0.1<(b+c)/b<10, and z=[2a+6(b+c)]/2. Theprecursor has x-ray diffraction peaks at d=2.53 and 1.70 Angstroms. Theprecursor is sulfided to produce the corresponding activated catalyst.

It is also within the scope of this disclosure that the gas-liquid flowto liquid-continuous aromatics saturation reactor 300 be blended understatic mixing conditions. By static mixing conditions we mean one ormore, preferably more, of geometric mixing elements fixed within a pipethat use the energy of the moving stream to create mixing between two ormore fluids. The advantage of the static mixers of the presentdisclosure over dynamic mixers, other than the fact that static mixershave no moving parts, is that static mixers split the stream hundreds,or even thousands of times, thus resulting in a continuous phasecontaining very fine droplets of discontinuous phase. This results in amuch larger surface area when compared with dynamic mixers. Thegas-liquid mixture can also be flashed in a suitable vessel beforeentering reactor 300 to remove at least a portion of any excess gas.Alternatively, excess gas can be vented (not shown) directly fromreactor 300.

To ensure that sufficient hydrogen is present in the liquid phase forreaction, and to mitigate coking, it may be necessary to recycle liquidproduct from the liquid-continuous aromatics saturation reactor 300. Therecycled liquid serves as a carrier for additional solubilized hydrogen.Alternatively, or in combination with this liquid recycle, hydrogen maybe added to the reactor by withdrawing liquid at one or more points,preferably at one or more axial points, along the reactor, resaturatingthe liquid with hydrogen, and reinjecting it back into the reactor. Thisapproach may be used to reduce the amount of liquid recycle required.

Because the liquid effluent from the reactor 300 contains only dissolvedgas, it is not necessary to have a high-pressure separation stepdownstream of the reactor. Only a low-pressure flash step is required tovent dissolved and excess gas before product fractionation. Eliminationof high-pressure product recovery vessels significantly reduces the costof the debottlenecking.

As previously mentioned, reactor 300 is operated such that the liquidphase represents the continuous phase in the reactor. Traditionally,hydroprocessing, including aromatics saturation, is conducted intrickle-bed reactors where an excess of gas results in a continuous gasphase in the reactor. In a liquid-continuous reactor, the feedstock isexposed to one or more beds of catalyst. The liquid hydrocrackatepreferably enters from the top or upper portions of the reactor andflows downward through the reactor. This downward liquid flow can assistin allowing the catalyst to remain in place in the catalyst bed.

A hydroprocessing process can typically involve exposing a feed to asuitable catalyst in the presence of hydrogen at effectivehydroprocessing conditions. Without being bound by any particulartheory, in a conventional trickle-bed reactor, the reactor can beoperated so that three “phases” are present in the reactor. Thehydroprocessing catalyst corresponds to the solid phase. Anothersubstantial portion of the reactor volume is occupied by a gas phase.This gas phase (second-phase) includes the hydrogen for hydroprocessing,optionally some diluent gases, and other gases such as contaminant gasesthat are formed during hydroprocessing. The amount of hydrogen gas inthe gas phase is typically present in substantial excess relative to theamount required for the hydroprocessing reaction. In a conventionaltrickle-bed reactor, the solid hydroprocessing catalyst and the gasphase can occupy at least 80% of the reactor volume, or at least 85%, orat least 90%. The third “phase” can correspond to the liquid feedstock.In a conventional trickle-bed reactor, the feedstock may only occupy asmall portion of the volume, such as less than 20%, or less than 10%, orless than 5%. As a result, the liquid feedstock may not form acontinuous phase. Instead, the liquid “phase” may include, for example,thin films of feedstock that coat the hydroprocessing catalystparticles.

Without being bound by any particular theory, a liquid-continuousreactor provides a different type of processing environment as comparedto a trickle-bed reactor. In a liquid-continuous reactor, the reactionzone is primarily composed of two phases. One phase is a solid phasecorresponding to the hydroprocessing catalyst, in this case an aromaticssaturation (ASAT) catalyst. The second phase is a liquid phasecorresponding to the hydrocrackate feedstock. The liquid feedstock phasewill be present as a continuous phase in the liquid-continuous reactorof the present disclosure. In an embodiment, the hydrogen that will beconsumed during the aromatic saturation reaction is dissolved in theliquid phase. Depending on the quantity of hydrogen used, a portion ofthe hydrogen can also be in the form of bubbles of hydrogen in theliquid phase. This hydrogen corresponds to hydrogen that is in additionto the hydrogen dissolved in the liquid phase. In another embodiment,hydrogen dissolved in the liquid phase can be depleted as the reactionsprogress in the liquid-continuous reactor. In such an embodiment,hydrogen initially present in the form of gaseous bubbles can dissolveinto the liquid phase to resaturate the liquid phase and provideadditional hydrogen for the reactions taking place in the reactor. Invarious embodiments, the volume occupied by a gas phase in theliquid-continuous reactor can be less than 10% of the reactor volume, oreven less than 5%.

The liquid feed to reactor 300 is preferably mixed with ahydrogen-containing treat gas. The hydrogen-containing treat gas willpreferably contain at least 50 vol % of hydrogen, more preferably atleast 80 vol %, even more preferably at least 90 vol %, and mostpreferably at least 95 vol %. Excess gas can be vented from the mixturebefore it enters the reactor, or excess gas can be vented directly fromthe reactor. The liquid level in the reactor is preferably controlled sothat the catalyst in the reactor is completely wetted.

In some embodiments, the hydroprocessing reactions in a bed, stage,and/or reactor can require more hydrogen than can be dissolved in aliquid. In such embodiments, one or more techniques can be used toprovide additional hydrogen for the hydroprocessing reaction. One optionis to recycle a portion of the product from the reactor. A recycledportion of product has already passed through a hydroprocessing stage,and therefore will likely have a reduced hydrogen consumption as itpasses again through the hydroprocessing stage. Additionally, thesolubility of the recycled feed can be higher than a comparableunprocessed feed. As a result, including a portion of recycled productwith fresh feed can increase the amount of hydrogen available forreaction with the fresh feed.

Another option can be to introduce additional streams of hydrogen intothe reactor directly. One or more additional hydrogen streams can beintroduced at any convenient location in the reactor. The additionalhydrogen streams can include a stream of make-up hydrogen, a stream ofrecycled hydrogen, or any other convenient hydrogen-containing stream.In some embodiments, both product recycle and injection of additionalhydrogen streams along the axial dimension of the reactor can be used toprovide sufficient hydrogen for a reaction.

In embodiments involving recycle of the product from liquid-continuousaromatics saturation zone 300 can be used as part of the input to theliquid-continuous aromatics saturation zone, or, reactor 300. The ratioof the amount by volume of product recycle to the amount of fresh feedinto the zone 300 can be at least 0.5 to 1, or at least 1 to 1, or atleast 1.5 to 1. The ratio of the amount by volume of product recycle tothe amount of fresh feed can be 5 to 1 or less, or 3 to 1 or less, or 2to 1 or less.

Aromatics saturation is performed by exposing a feedstock to anaromatics saturation catalyst under effective aromatics saturationconditions. Effective aromatics saturation conditions can include atemperature of at least 400° F. (204° C.), or at least 450° F. (232°C.), or at least 500° F. (260° C.). Alternatively, the temperature canbe 750° F. (399° C.) or less, or 700° F. (371° C.) or less, or 650° F.(343° C.) or less. The pressure can be at least 500 psig (3.3 MPa), orat least 800 psig (5.3 MPa), or at least 1000 psig (6.6 MPa).Alternatively, the pressure can be 2500 psig (16.6 MPa) or less, or 2000psig (13.3 MPa) or less, or 1500 psig (10 MPa) or less. The liquidhourly space velocity (LHSV) over the dewaxing catalyst can be at least0.25 hr⁻¹, or at least 0.5 hr⁻¹, or at least 0.75 hr⁻¹. Alternatively,the LHSV can be 15 hr⁻¹ or less, or hr⁻¹ or less, or 5 hr⁻¹ or less. Instill another embodiment, the temperature, pressure, and LHSV for aliquid-continuous reactor can be conditions suitable for use in atrickle-bed reactor.

In embodiments where excess gas is vented from the liquid effluent, theavailable hydrogen in the reactor will correspond to the amount ofhydrogen dissolved in the liquid. Thus, a higher treat gas rate may notlead to an increase in the amount of available hydrogen. In such asituation, the effective treat gas rate within a reactor may bedependent on the solubility limit of the feedstock. The hydrogensolubility limit for a typical hydrocarbon feedstock is 30 scf/bbl to200 scf/bbl.

One advantage of a liquid-continuous reactor is that a large excess ofhydrogen is not fed to the reactor. The use of a large excess ofhydrogen typically requires complex and expensive separation equipmentto allow for recovery, and often recycling, of the excess hydrogen.Typically, the recycle compressor used for hydrogen recycle in atrickle-bed reactor corresponds to 10 to 15 wt. % of the total cost ofthe processing unit. Instead, it is desirable for a liquid-continuousreactor will desirably supply only an amount of hydrogen comparable tothe amount needed for a hydroprocessing reaction and to mitigatecatalyst coking.

Returning now to the FIGURE hereof, the effluent stream from 300 isconducted via line 18 to fractionator 400 wherein a lube oil liquideffluent fraction is separated and passed via line 20 to catalyticdewaxing stage 500. Make-up hydrogen-containing treat gas can beintroduced via line 24 when needed. Any predetermined additionalfractions can be separated and are collected from fractionator 400 vialines 22. It will be understood that catalytic dewaxing stage 500 canalso be operated in liquid-continuous mode. It is within the scope ofthis disclosure that the liquid effluent from the liquid-continuousaromatics saturation zone can be conducted directly to catalyticdewaxing and the effluent from catalytic dewaxing fractionated.

Catalytic dewaxing can be performed by exposing the feedstock to adewaxing catalyst under effective (catalytic) dewaxing conditions.Effective dewaxing conditions can include a temperature of at least 500°F. (260° C.), or at least 550° F. (288° C.), or at least 600° F. (316°C.), or at least 650° F. (343° C.). Alternatively, the temperature canbe 750° F. (399° C.) or less, or 700° F. (371° C.) or less, or 650° F.(343° C.) or less. The pressure can be at least 200 psig (1.4 MPa), orat least 400 psig (2.8 MPa), or at least 750 psig (5.2 MPa), or at least1000 psig (6.9 MPa). Alternatively, the pressure can be 1500 psig (10.3MPa) or less, or 1200 psig (8.2 MPa) or less, or 1000 psig (6.9 MPa) orless, or 800 psig (5.5 MPa) or less. The liquid hourly space velocity(LHSV) over the dewaxing catalyst can be at least 0.1 hr⁻¹, or at least0.2 hr⁻¹, or at least 0.5 hr⁻¹, or at least 1.0 hr⁻¹, or at least 1.5hr⁻¹. Alternatively, the LHSV can be 10.0 hr⁻¹ or less, or 5.0 hr⁻¹ orless, or 3.0 hr⁻¹ or less, or 2.0 hr⁻¹ or less. In still anotherembodiment, the temperature, pressure, and LHSV for a liquid-continuousreactor can be the same conditions typically used for a trickle-bedreactor.

Catalytic dewaxing involves the removal and/or isomerization of longchain, paraffinic molecules from feeds. Catalytic dewaxing can beaccomplished by selective cracking or by hydroisomerizing these linearmolecules. Hydrodewaxing catalysts can be selected from molecular sievessuch as crystalline aluminosilicates (zeolites) orsilico-aluminophosphates (SAPOs). In an embodiment, the molecular sievecan be a 1-D or 3-D molecular sieve. In another embodiment, themolecular sieve can be a 10-member ring 1-D molecular sieve. Examples ofmolecular sieves which have shown dewaxing activity in the literaturecan include ZSM-48, ZSM-22, ZSM-23, ZSM-35, Beta, USY, ZSM-5, andcombinations thereof. In an embodiment, the molecular sieve can beZSM-22, ZSM-23, ZSM-35, ZSM-48, or a combination thereof. In stillanother embodiment, the molecular sieve can be ZSM-48, ZSM-23, ZSM-5, ora combination thereof. In yet another embodiment, the molecular sievecan be ZSM-48, ZSM-23, or a combination thereof. Optionally, thedewaxing catalyst can include a binder for the molecular sieve, such asalumina, titania, silica, silica-alumina, zirconia, or a combinationthereof.

One feature of molecular sieves that can impact the activity of themolecular sieve is the ratio of silica to alumina in the molecularsieve. In an embodiment, the molecular sieve can have a silica toalumina ratio of 200 to 1 or less, or 120 to 1 or less, or 100 to 1 orless, or 90 to 1 or less, or 75 to 1 or less. In an embodiment, themolecular sieve can have a silica to alumina ratio of at least 30 to 1,or at least 50 to 1, or at least 65 to 1.

The dewaxing catalyst can also include a metal hydrogenation component,such as a Group VIII metal. Suitable Group VIII metals can include Pt,Pd, Ni, or a combination thereof.

The dewaxing catalyst can include at least 0.1 wt % of a Group VIIImetal, or at least 0.3 wt %, or at least 0.5 wt %, or at least 1.0 wt %,or at least 2.5 wt %, or at least 5.0 wt %. Alternatively, the dewaxingcatalyst can include 10.0 wt % or less of a Group VIII metal, or 5.0 wt% or less, or 2.5 wt % or less, or 1.5 wt % or less, or 1.0 wt % orless.

In some embodiments, the dewaxing catalyst can also include at least oneGroup VIB metal, such as W or Mo. Such Group VIB metals are typicallyused in conjunction with at least one Group VIII metal, such as Ni orCo. An example of such an embodiment is a dewaxing catalyst thatincludes Ni and W, Mo, or a combination of W and Mo. In such anembodiment, the dewaxing catalyst can include at least 0.5 wt % of aGroup VIB metal, or at least 1.0 wt %, or at least 2.5 wt %, or at least5.0 wt %. Alternatively, the dewaxing catalyst can include 20.0 wt % orless of a Group VIB metal, or 15.0 wt % or less, or 10.0 wt % or less,or 5.0 wt % or less, or 1.0 wt % or less. In an embodiment, the dewaxingcatalyst can include Pt, Pd, or a combination thereof. In anotherembodiment, the dewaxing catalyst can include Co and Mo, Ni and W, Niand Mo, or Ni, W, and Mo.

The catalytic dewaxer can be operated at pressures significantly lowerthan the hydrocracker. That is, at least 300 psi, or at least 500 psi,and even at least 1000 psi lower than the hydrocracking stage. Bothstages being high pressure is far more common and consistent with highquality lube production.

Returning again to the FIGURE hereof, the effluent from catalyticdewaxing stage 500 is sent to hydrofinishing stage 600. Thehydrofinishing step following dewaxing offers further opportunity toimprove product quality without significantly affecting its pour point.Hydrofinishing is a mild, relatively cold hydrotreating process, thatemploys a catalyst, hydrogen and mild reaction conditions to removetrace amounts of heteroatom compounds, aromatics and olefins, to improveprimarily oxidation stability and color. Hydrofinishing reactionconditions include temperatures from 300° F. to 675° F. (149° C. to 357°C.), preferably from 300° F. to 480° F. (149° C. to 249° C.), a totalpressure of from 400 to 3000 psig (2859 to 20786 kPa), a liquid hourlyspace velocity ranging from 0.1 to 5 LHSV (hr⁻¹), preferably 0.5 to 3hr⁻¹. The hydrotreating catalyst will comprise a support component andone or more catalytic metal components. The one or more metals areselected from Group VIB (Mo, W, Cr) and Group VIII (Ni, Co and the noblemetals Pt and Pd). The metal or metals may be present from as little as0.1 wt % for noble metals, to as high as 30 wt % of the catalystcomposition for non-noble metals. Preferred support materials are low inacid and include, for example, amorphous or crystalline metal oxidessuch as alumina, silica, silica alumina and ultra large pore crystallinematerials known as mesoporous crystalline materials, of which MCM-41 isa preferred support component. Unsupported base metal (non-noble metal)catalysts are also applicable as hydrofinishing catalysts.

The effluent stream from hydrofinishing zone 600 is passed via line 26to second separation zone 700 wherein a gaseous effluent stream isseparated from the resulting liquid phase lube oil base stock. Thegaseous effluent stream, a portion of which will be unreactedhydrogen-containing treat gas can be recycled via line 28 tohydrocracking stage 100. The resulting lube oil base stock, which willmeet Group II or Group III base oil requirements, is collected via line30.

All patents and patent applications, test procedures (such as ASTMmethods, UL methods, and the like), and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this disclosure and for all jurisdictions in whichsuch incorporation is permitted.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.While the illustrative embodiments of the disclosure have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of thedisclosure. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present disclosure,including all features which would be treated as equivalents thereof bythose skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference tonumerous embodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. A process for the production of high quality lube base oils, whichprocess comprising: i) hydrocracking a lube oil feedstock having aboiling point above 600° F. and containing polycyclic aromatics in thepresence of hydrogen and a hydrocracking catalyst to produce ahydrocrackate having a boiling point above 600° F. which hydrocrackatecontains a lesser amount of polycyclic aromatics than said lube oilfeedstock; ii) hydrotreating at least a portion of said hydrocrackate inthe presence of an aromatics saturation catalyst under effectivearomatics saturation conditions in a liquid-continuous reactor to form ahydrotreated hydrocrackate having a waxy paraffinic component; and iii)catalytically dewaxing said hydrotreated hydrocrackate in the presenceof hydrogen and a dewaxing catalyst under effective dewaxing conditionsincluding a temperature from 500° F. to 750° F. and a pressure up to2200 psig and at an effective contact time of feed to catalyst that willremove at least a portion of the waxy paraffinic components byisomerization to less waxy iso-paraffinic components, thereby producinga lube base oil containing of at least 90 wt. % saturates, less than0.03 wt. % sulfur and a viscosity index of at least
 80. 2. The processof claim 1 wherein the lube oil feedstock is selected from the groupconsisting of vacuum gas oils, hydrocracked gas oils, hydrocrackedvacuum gas oils, deasphalted oils, slack waxes, foots oils, coker towerbottoms, reduced crude, vacuum tower bottoms, deasphalted vacuum resids,fluid catalytic cracking tower bottoms, and cycle oils.
 3. The processof claim 2 wherein the lube oil feedstock is a vacuum gas oil.
 4. Theprocess of claim 1 wherein a portion of the hydrotreated hydrocrackateis recycled to the liquid-continuous reactor and again hydrotreated withfresh hydrocrackate.
 5. The process of claim 4 wherein the volume ratioof recycled hydrotreated hydrocrackate to fresh hydrocrackate to theliquid-continuous reactor is from 0.5 to 1 to 5 to
 1. 6. The process ofclaim 4 wherein the volume ratio of recycled hydrotreated hydrocrackateto fresh hydrocrackate to the liquid-continuous reactor is from 1 to 1to 3 to
 1. 7. The process of claim 1 wherein a portion of thehydrotreated hydrocrackate from the liquid-continuous reactor iswithdrawn and saturated with hydrogen then recycled back to theliquid-continuous reactor.
 8. The process of claim 1 wherein thearomatics saturation catalyst is comprised of one or more catalyticmetals selected from Groups VIB and Group VIII of the Periodic Table ofthe Elements on an amorphous or crystalline refractory support.
 9. Theprocess of claim 8 wherein the support is a mesoporous material.
 10. Theprocess of claim 9 wherein the mesoporous material is MCM-41.
 11. Theprocess of claim 9 wherein the catalytic metal is selected from thegroup consisting of Pt and Pd.
 12. The process of claim 1 wherein thehydrocracking of step i) results in at least a 50% reduction ofaromatics compared to the amount of aromatics in the lube oil feedstock.13. The process of claim 1 wherein the process conditions for aromaticssaturation during hydrotreating includes temperatures from 400° F. to750° F. and pressures from 500 psig to 2500 psig.
 14. The process ofclaim 1 wherein the catalytic dewaxing temperature is from 500° F. to750° F.
 15. The process of claim 1 wherein the catalytic dewaxingcatalyst is selected from the group consisting of crystallinealuminosilicates and silicoaluminophosphates.
 16. The process of claim15 wherein the catalytic dewaxing catalyst is a crystallinealuminosilicate selected from the group consisting of ZSM-22, ZSM-23,ZSM-35 and ZSM-48, and combinations thereof.
 17. The process of claim 16wherein the catalytic dewaxing catalyst contains a binder materialselected from the group consisting of alumina, titania, silica,silica-alumina, zirconia, and combinations thereof.
 18. The process ofclaim 16 wherein the catalytic dewaxing catalyst contains at least onemetal selected from the group consisting of Pt, Pd, and Ni.
 19. Theprocess of claim 18 wherein the catalytic dewaxing catalyst alsocontains a metal selected from W and Mo.
 20. The process of claim 1wherein the dewaxed lube oil is subjected to hydrofinishing in thepresence of hydrogen and a hydrofinishing catalyst at a temperature from300° F. to 675° F. and total pressures from 400 to 3000 psig.
 21. Theprocess of claim 20 wherein the hydrofinishing catalyst is comprised ofone or more metals selected from Group VIII and Group VIB of thePeriodic Table of the Elements.
 22. The process of claim 21 wherein thehydrofinishing catalyst contains at least one metal from Group VIII andat least one metal from Group VIB.
 23. The process of claim 21 whereinthe hydrofinishing catalyst is comprised of a noble metal selected fromPt and Pd on a mesoporous crystalline support.
 24. The process of claim23 wherein the mesoporous crystalline support is MCM-41.
 25. A processfor the production of high quality lube base oils, which processcomprising: i) hydrocracking a lube oil feedstock having a boiling pointabove 600° F. and containing polycyclic aromatics in the presence ofhydrogen and a hydrocracking catalyst to produce a hydrocrackate havinga boiling point above 600° F. which contains a lesser amount ofpolycyclic aromatics than said lube oil feedstock; ii) hydrotreating atleast a portion of said hydrocrackate in the presence of an aromaticssaturation catalyst under effective aromatics saturation conditions in aliquid-continuous reactor to form a hydrotreated hydrocrackate having awaxy paraffinic component; iii) catalytically dewaxing said hydrotreatedhydrocrackate in the presence of hydrogen and a dewaxing catalyst undereffective dewaxing conditions including a temperature from 500° F. to750° F. and a pressure up to 2200 psig and at an effective contact timeof feed to catalyst that will remove at least a portion of the waxyparaffinic components by isomerization to less waxy iso-paraffiniccomponents; and iv) subjecting the dewaxed hydrotreated hydrocrackate tohydrofinishing in the presence of hydrogen and a hydrofinishing catalystand at hydrofinishing conditions thereby resulting in a lube base oilcomprised of at least 90 wt. % saturates, less than 0.03 wt. % sulfurand a viscosity index of at least
 80. 26. The process of claim 25wherein the lube oil feedstock is selected from the group consisting ofvacuum gas oils, hydrocracked gas oils, hydrocracked vacuum gas oils,deasphalted oils, slack waxes, foots oils, coker tower bottoms, reducedcrude, vacuum tower bottoms, deasphalted vacuum resids, fluid catalyticcracking tower bottoms, and cycle oils.
 27. The process of claim 26wherein the lube oil feedstock is a vacuum gas oil.
 28. The process ofclaim 26 wherein a portion of the hydrotreated hydrocrackate is recycledto the liquid-continuous reactor and again hydrotreated with freshhydrocrackate.
 29. The process of claim 28 wherein the volume ratio ofrecycled hydrotreated hydrocrackate to fresh hydrocrackate to theliquid-continuous reactor is from 0.5 to 1 to 5 to
 1. 30. The process ofclaim 28 wherein the volume ratio of recycled hydrotreated hydrocrackateto fresh hydrocrackate to the liquid-continuous reactor is from 1 to 1to 3 to
 1. 31. The process of claim 25 wherein a portion of thehydrotreated hydrocrackate from the liquid-continuous reactor iswithdrawn and saturated with hydrogen then recycled back to theliquid-continuous reactor.
 32. The process of claim 25 wherein thearomatics saturation catalyst is comprised of one or more catalyticmetals selected from Groups VIB and Group VIII of the Periodic Table ofthe Elements on an amorphous or crystalline refractory support.
 33. Theprocess of claim 32 wherein the support is a mesoporous material. 34.The process of claim 33 wherein the mesoporous material is MCM-41. 35.The process of claim 33 wherein the catalytic metal is selected from thegroup consisting of Pt and Pd.
 36. The process of claim 25 wherein thehydrocracking of step i) results in at least a 50% reduction ofaromatics compared to the amount of aromatics in the lube oil feedstock.37. The process of claim 25 wherein the process conditions for aromaticssaturation during hydrotreating includes temperatures from 400° F. to750° F. and pressures from 500 psig to 2500 psig.
 38. The process ofclaim 25 wherein the catalytic dewaxing temperature is from 500° F. to750° F.
 39. The process of claim 25 wherein the catalytic dewaxingcatalyst are selected from the group consisting of crystallinealuminosilicates and silicoaluminophosphates.
 40. The process of claim39 wherein the catalytic dewaxing catalyst is a crystallinealuminosilicate selected from the group consisting of ZSM-22, ZSM-23,ZSM-35 and ZSM-48, and combinations thereof.
 41. The process of claim 40wherein the catalytic dewaxing catalyst contains a binder materialselected from the group consisting of alumina, titania, silica,silica-alumina, zirconia, and combinations thereof.
 42. The process ofclaim 40 wherein the catalytic dewaxing catalyst contains at least onemetal selected from the group consisting of Pt, Pd, and Ni.
 43. Theprocess of claim 42 wherein the catalytic dewaxing catalyst alsocontains a metal selected from W and Mo.
 44. The process of claim 25wherein the hydrofinishing catalyst is comprised of one or more metalsselected from Group VIII and Group VI of the Periodic Table of theElements.
 45. The process of claim 44 wherein the hydrofinishingcatalyst contains at least one metal from Group VIII and at least onemetal from Group VIB.
 46. The process of claim 44 wherein thehydrofinishing catalyst is comprised of a noble metal selected from Ptand Pd on a mesoporous crystalline support.
 47. The process of claim 46wherein the mesoporous crystalline support is MCM-41.